Petroleum is typically found in subterranean formations in which it has accumulated, having been formed by entrapped organic matter that is buried in the earth as geological changes occur. Wells are drilled from the earth's surface to penetrate the hydrocarbon (petroleum) bearing formations. Most formations, in their natural state, contain the hydrocarbons under pressure, that is, there is formation pressure so that initially when a borehole penetrates a formation, sufficient subterranean pressure exists to force the flow of oil and/or gas to the earth's surface. However, in many hydrocarbon formations the subterranean pressure eventually is reduced as oil and/or gas are withdrawn from the formation. When the formation pressure is insufficient to force hydrocarbon fluids to the earth's surface in commercial quantities, they must be pumped. While liquid petroleum can be pumped to the earth's surface by a variety of pumping means, one of the most commonly employed is that using a reciprocating pump that is positioned within a tubing string extending from the earth's surface to the producing formation. The pump is typically actuated by a string of sucker rods that are reciprocated within the tubing string. The lower end of the sucker rod string is attached to the pump. The upper end of the sucker rod string extends to, or at least approximately to, the earth's surface. At the earth's surface some means must be provided to accommodate the reciprocation of the sucker rod string and yet permit pumped fluid to pass from the top of the tubing string for collection. For this purpose, a pumping "T" is attached to the upper end of the tubing string providing a connection for a leadline, or other conduit, to carry produced fluids and/or gases away from the well. Attached to the top of the pumping "T" is a stuffing box. Reciprocated within the stuffing box is a cylindrical polished rod having a smooth outer surface. The lower end of the polished rod is attached to the upper end of the sucker rod string, and the upper end is secured to a pumping unit so that the polished rod is reciprocated vertically within the stuffing box to thereby reciprocate the sucker rod string and the pump attached to it. Packing within the stuffing box surrounds the polished rod to retain produced fluids and gases. The polished rod must be constructed of material specifically selected to provide the tensile strength required for the reciprocation of a string of sucker rods; accordingly, most polished rods are made of steel.
For many years it has been a custom in the petroleum industry to employ polished rod liners on the exterior of the polished rod. Polished rod liners are made of material having good wear characteristics to receive the rubbing action of the packing within the stuffing box, and a polished rod liner does not have to be of high strength material since tensile strength is not important.
In recent years, increased environmental concern has arisen in the petroleum industry. A major concern is that of the escape of hydrocarbons (fluids or gases) in the event of breakage of a polished rod. That is, if the polished rod breaks or if the polished rod comes lose from the mechanism that attaches it to the pumping unit by which it is reciprocated, the polished rod can fall downwardly through the stuffing box, leaving the stuffing box completely open so that hydrocarbons can escape to the atmosphere. To combat this problem, others have provided safety valves within the stuffing box that close in the event that a polished rod should break or otherwise be removed from the stuffing box. For examples of devices to prevent the escape of hydrocarbons in the event that a polished rod is inadvertently withdrawn from a stuffing box, see U.S. Pat. No. 5,141,052 entitled "Well Head Stuffing Box For Polished Rod and Accessories For Same" issued Aug. 25, 1992.
Another stuffing box having an integral valve with a mechanism for closing in the event that the polished rod falls out of the stuffing box is U.S. Pat. No. 4,907,650 entitled "Well Head For Safety Valve For Pumping Well" issued Mar. 13, 1990. For further background to this type of device the following patents are also relevant: U.S. Pat. Nos. 3,939,910; 4,109,713; 4,099,562; 1,708,261 and 4,889,184.
These prior issued patents are representative of the state of the art relating to the prevention of the escape of hydrocarbons from a well in the event of loss of a polished rod. However, the devices revealed in the prior issued patents will not function if a polished rod liner is used on a polished rod. If a polished rod is removed from a well pumping system that employs a polished rod liner, the polished rod liner can be left within the stuffing box, providing an open passageway for the escape of hydrocarbons. With the polished rod liner remaining in the stuffing box, the closure devices, as illustrated in the above mentioned patents, cannot close and, therefore, fluids and/or gases are free to escape.
A basic object of this invention is to provide a polished rod liner head for use in attaching a polished rod liner to a polished rod that will automatically close the passageway through the polished rod liner in the event the polished rod is removed to thereby prevent the flow of fluids or gases through the polished rod liner.
Another basic object is to provide a polished rod liner head having means to prevent the polished rod from slipping out of the head in the event the polished rod breaks above the polished rod liner or become loose from the polished rod clamp.